Fixed errors and added missing function

There is no function getDevices, it's listDevices. The first argument in the callback seems to be `err`, and not `devices`.
Also found the method I *actually* wanted in the source code, `getDevice` by it's id. So I added a short doc for it as well.
Chagned "lets" to "let's"

because in this usage it's a contractor for "let us".
Merge pull request #256 from KatieK2/patch-1

Chagned "lets" to "let's"
Merge pull request #254 from gregersrygg/patch-1

Fixed errors and added missing function for SparkJS
corrected tmp36 schematic

fixes: https://github.com/spark/docs/issues/252
adding list of properties for get-event-stream callback
Merge branch 'master' of https://github.com/spark/docs